Tobacco Smoking Filter or Filter Element with a Content of Adjuncts

ABSTRACT

A tobacco smoking filter is disclosed, with adjunets on the surface in the form of fibres filaments or films and whereby the drawing resistance of the tobacco smoking filter and the mass of the adjuncts in the tobacco smoking filter meet the following equation (I) M ad /Δp&gt;1 mg/daPA (I), where Δp is the drawing resistance [daPA], applied as a value calculated with a 7.8 mm filter diameter and M ad  [mg] is the mass of the adjuncts. The tobacco smoking filter comprises channel structures and the filer material is provided as a planar material. Said tobacco smoking filter has a low draw resistance on smoking with a particularly good filtration effect and is relatively simple to produce.

The invention relates to tobacco smoke filters or filter elements, whichare constructed in one piece and contain fibers, filaments or filmsbased on polymers or polymer mixtures, which can be spun or processedinto films, and contain one or more additives.

Tobacco smoke filters of the above type are known in the art. In thisconnection, “in one piece” is to be understood that the tobacco smokefilters are constructed uniformly in the longitudinal axial directionand can be produced without further limiting filter elements. Here thereis a relevant difference from so-called “chamber filters”, for which anoutwardly limited chamber is created by an enveloping paper betweenfilter elements of conventional filter material, disposed at a distancefrom one another in the longitudinal direction. This chamber may befilled with additives, such as granular activated charcoal.

There has been no lack of attempts to design filter construction, whichpermit a particularly efficient utilization of porous elements. Thechamber filter construction named has disadvantages in the efficientutilization of the included activated charcoal. Because of thelimitation to the degree, to which the chamber can be filled, and due tothe comparatively coarse granulation of the activated charcoal, aportion of the smoke passes through that part of the chamber, which isnot filled, and, accordingly, does not come into direct contact with theactivated charcoal. The particle size of the activated charcoal cannotbe reduced at will, since this would result in an increase in theresistance to airflow, which is not acceptable to the smoker. The filterconstruction, described in the EPA-O 014 477 behaves more advantageouslyin this respect. For this construction, the granular activated charcoalis scattered into a filter element in a manner that assures anapproximately homogeneous distribution of the activated charcoalparticles in the fibers or filaments of the filter material, which, inturn, are distributed homogeneously. Even though the formation of abypass can be excluded in this manner, coarsely grained additives arenevertheless required, in order to ensure that the aforementionedparticles are fixed in the tobacco smoke filter. The disadvantages,ascribed to coarsely grained activated charcoal, are therefore alsoexhibited by this filter construction.

The following may be mentioned in connection with tobacco smoke filtersor their use and as a background for the invention, which is describedbelow. At their mouth end, filter cigarettes are provided with tobaccosmoke filters, which intercept at least a portion of the combustionproducts of the tobacco of the cigarette and, by so doing, preventinhalation of the combustion products during smoking. On the other hand,a tobacco smoke filter should affect the taste of the tobacco smoke, sothat it is evaluated positively by the smoker. For a portion of filtercigarettes, the tobacco smoke filter is treated with a porous,particulate additive, which increases the filtration performance of thetobacco smoke filter or the tobacco smoke filter elements in comparisonto a tobacco smoke filter without the particulate additives. This effectfrequently can be explained owing to the fact that the porous additivespreferentially adsorb gaseous combustion products at their inner surfaceand, by so doing, reduce their concentration in the smoke. For the mostprominent representatives of this type of cigarette filters, activatedcharcoal is used as porous, particulate additive. Other tobacco smokefilters, such as those described in the DE-A-2 658 479, contain oxides,hydroxides and/or oxide hydrates of different metals, such as silicon,aluminum, magnesium, iron and/or titanium. The accessibility of suchporous, particulate additives for the gaseous smoke components is ofdecisive importance for their effectiveness. For example, it has turnedout the filter performance of finely divided porous materials especiallyis better than that of coarser particles. Further disadvantages of thechamber filters addressed are to be seen therein that the cost ofmanufacturing them are high.

Other known filter constructions indicate possibilities of binding alsofinely grained additives in the tobacco smoke filters. U.S. Pat. Nos.3,043,736 and 2,881,770 describe a tobacco smoke filter consisting of abundle of endless crimped filaments of cellulose acetate, which has beencombined into a filter rod by enveloping paper, the individual filamentsbeing coated with finely divided activated charcoal. The possibledevices for applying the finely particulate additives can be dividedinto devices a) for applying the additives from a suspension in anaqueous phase or a volatile organic carrier or a plasticizer fluid, b)for blowing-on the additives, which consist of small particles and maypreviously be wetted with an adhesive or a plasticizer, c) for applyingfrom a latex emulsion and d) for applying the additive, in that a bundleof filaments or threads, previously wetted with adhesive or plasticizer,is passed through a whirled-up bed of finely divided activated charcoal.In this respect, reference is made to the DE 127 4 946.

The tobacco smoke filters, produced according to the above method, aredistinguished owing to the fact that the filaments, loaded withadditives, are oriented preferably longitudinally and are bound to oneanother alternately at statistically distributed contact sites by meansof the action of an adhesive or plasticizer, so that essentiallylongitudinal, small spaces, distributed uniformly over the filter, arecreated between adjacent filaments by the flow of the tobacco smoke.

The examples listed make it clear that the tobacco smoke filters, soproduced and treated with particulate additives, have a high resistanceto the flow of air, which is similar to that of comparison filters, inwhich particulate additives have not been enmeshed. Accordingly,filters, which have a uniformly high mass of additives as well as a lowresistance to airflow, cannot be produced according to these methods.

Alternatively, paper filters, doped with activated charcoal, are used intobacco smoke filters. These contain activated charcoals of smallparticle size, which are bound to the paper during thepaper-manufacturing process. At the same time, during the production ofthe filter material, a fabric is formed, rolled onto bobbins andsubsequently sent to the processor. The filter or cigarette manufacturerunrolls the material from the bobbins and forms it into a rod-shapedproduct, in order to consolidate it then transversely axially in themold part of the filter rod machine, envelop it in paper and cut it tothe ultimate length of the filter rods. In addition, the fabric usually,but not necessarily, is wrinkled parallel to the direction in which itruns through the creping device, before it is shaped into a rod. Withthat, a reduction in the density of the material on the one hand, and aneffect on the resistance to the passage of air through the filter on theother, are achieved. A channel structure, in which longitudinallyaligned, channel-shaped regions of low material density extend over aconsiderable portion of the filter or filter element, is characteristicof such filters produced by folding two-dimensional materials. Thesechannels are bounded by filter material of a higher material density.The comparatively low resistance of these filters to the passage of aircan be attributed essentially to this structural property.

However, when these two-dimensional filters, which do not consist orconsist only partially of cellulose acetate, are used, the taste of thesmoke frequently is evaluated as being negative. In addition, suchfilters do not exhibit the specific retention performances for phenolsor nitrosamines, which are known from cigarette filters of celluloseacetate.

It was therefore an object of the invention to improve the tobacco smokefilters or filter elements, which are constructed in one piece anddescribed above, so that the effectiveness of the bonded, finely dividedabsorbents is effected as little as possible, and, nevertheless, when ahigher mass of the particulate additives are bonded, the resistance tothe passage of air is low. Moreover, cellulose acetate, in particular,is to be used as filter material.

Pursuant to the invention, this objective is accomplished owing to thefact that that a) the additives are present on the surface of thefibers, the filaments or the films, b) the resistance of the tobaccosmoke filter to the passage of air and the mass of the additives in thetobacco smoke filter observe the following equation (I): M_(ad)/ΔP>1mg/daPA (I), in which ΔP is the resistance to the passage of air (daPA),which is used as a value calculated on the basis of a 7.8 mm filterdiameter, M_(ad)(mg) is the mass of the additives, c) the tobacco smokefilter has a channel structure and d) the filter material is present asa two-dimensional formation.

Within the scope of the invention, the usual fibers, filaments andfilms, based on polymers or polymer mixtures, which can be spun orprocessed into films, may be used. Within the scope of the invention,the filter material preferably is a two-dimensional structure of fibersor filaments or a film, the two-dimensional structure and/or the filmbeing smooth, folded, embossed and/or partially consolidated.

It is particularly preferred if the filter material is built up from acellulose ester, cellulose acetate, cellulose butyrate, celluloseacetobutyrate, cellulose acetopropionate and/or cellulose propionate, inparticular, coming into consideration as cellulose ester. A particularlypreferred cellulose acetate has a degree of substitution of 1.5 to 3.0,especially of about 2.2 to 2.6 and, particularly of 2.5. Within thescope of the invention or of its realization, it has proven to beparticularly advantageous to use a tobacco smoke filter, which isdescribed in WO 01/28369. In a slight modification of the presentinvention and for the further optimization, it is preferred that thefiber weight (or filament weight resistance to the passage of air ratioS), related to the filament funnel, is larger than about 0.7, the Svalue being calculated from the formula

S=(m _(A))/Δp _(7.8)/dpf(10 m/daPA)   (II),

in which m_(A) is the fiber weight (g) ΔP (sic!!) is the resistance tothe passage of air (daPA) and dpf is the filament titer (dtex) and, forthe resistance to the passage of air, the value, calculated for a filterdiameter of 7.8 mm, is used, and the hardness of the cigarette filterexceeds approximately 90 filtrona hardness.

Moreover, it is regarded as preferred here that the fiber weight doesnot exceed 10 mg/mm of filter length and/or the residual crimping of thefilter material does not exceed the value of 1.45, the following formula(III) applying here:

I _(r)=10,000×m _(A)/(G×I)   (III),

in which m_(A) is the fiber weight (g), G is the total titer (g/10 exp4×m) and I is the filter length (mm).

The optimum residual crimping is between 1.05 and 1.4 and especiallybetween 1.1 and 1.3. Moreover, preferably the fiber weight (or filamentweight)/resistance to the passage of air ratio S, related to thefilament titer, does not exceed a value of about 2 and, in particular,has a value between 0.8 and 1.3.

Particularly advantageous results are achieved with the inventivetobacco smoke filter if the fiber weight (or filament weight) is atleast 4 mg/mm of filter length and especially between about 5 and 8mg/mm of filter length.

With respect to optimizing the filtrona hardness, it may be noted thatthis should preferably be between about 90 and 95 and particularlybetween 91 and 93.

Within the scope of the invention, the additives, which are essentialfor accomplishing the objectives set, are disposed on the surface of thefibers, the filaments or the films. It is particularly preferred here ifthese additives are particulate and, in particular, have a particle sizeof less than 300 μm and especially of less than 100 μm. It isparticularly preferred if the particle diameter is less than 50 μm, aparticle size of 30 μm leading to particularly good results. Theinvention is not subject to any significant limitation in the selectionof the particulate additives or porous additives. Someone of ordinary ofskill in the art is capable of selecting suitable additives without anyproblems, these being present preferably in the form of an adsorbentbased on activated charcoal, metal oxides, metal hydroxides and/or metaloxide hydrates, especially those of aluminum, silicon, titanium and/ormagnesium. In individual cases, the porous additive preferably istreated additionally with active substances, especially in the form ofantioxidants, flavors and/or anti-mutagenic substances.

The introduction of the particulate additives into the inventive tobaccosmoke filter is not limited critically. Nevertheless, it is preferred ifthe particulate additives are fixed to the surface of the filtermaterial by means of a binder, especially with polyvinyl acetate,polyvinyl alcohol, polyethylene glycol, water-soluble esters or ethers,starch, starch derivatives and/or cellulose esters.

The surface of the fibers, filaments and films may be optimized further,as follows. For example, the additive on the surface may fulfill thefunction of a filtration aid, especially in the form of organic acids,acidic carboxylic esters, of polyphenol and/or porphyrin derivatives.The fibers, filaments and films of the film material or the fibers,filaments and films, from which the tobacco smoke filters or filterelements are built up, may contain in their interior further additives,which improve their properties. Preferably, these are plasticizers,frosting agents, pigments and/or stabilizers. The inclusion ofplasticizers is of particular importance. Preferably, these are presentwithin the fibers or filaments or films in an amount of 0 to 15% byweight and especially of 5 to 12% by weight. Advisably, the plasticizeris present as triacetin, ethylene glycol diacetate and/or diethylcitrate. In addition, the inventive tobacco smoke filter may alsocontain a photoreactive additive, especially in the form of a finelydivided titanium dioxide of the anatase type, having an average particlesize of less than 2 μm.

A particular characteristic is given by the distinguishing feature b) ofthe above-defined inventive teachings. According to this, it is arequirement of the invention that the resistance to the flow of air ofthe tobacco smoke filter and the mass of the additive in the tobaccosmoke filter adhere to the following formula M_(ad)/ΔP_(7.8)>1 mg/daPA(I), in which ΔP is the resistance to the passage of air (daPA), whichis used as a value calculated on the basis of a 7.8 mm filter diameter,M_(ad)(mg) is the mass of the additives. In particular, it is preferredif the ratio of M_(ad)/ΔP is more than 2 mg/daPa and, in particular,more than 3 mg/daPa.

The channel structure of the claimed, one-piece tobacco smoke filter orfilter elements is a further significant distinguishing feature of theinvention. It should be pointed out that, for a channel structure,longitudinally aligned, channel-shaped regions of lower material densityextend over an appreciable part of the filter or filter element. Thesechannels are limited by the filter material of a higher materialdensity. In particular, this channel structure is adhered to owing tothe fact that a two-dimensional formation is used, pursuant to theinvention, as filter material.

Someone of ordinary skill in the art can, without problems and withoutfurther additional technical information, produce the one-piece tobaccosmoke filter or the one-piece tobacco smoke filter element. Aparticularly suitable method is dealt with in the following. Here, forthe production of the inventive tobacco smoke filter tow is pulled frombales, prepared pneumatically according to methods customary for spacefilters. Before the actual activation step, a nonwoven fabric, with thehighest possible strength in the direction of the two axes of thesurface, is produced in an intermediate step, wound onto spools andacted upon with additives. Any method, suitable for producing tobaccosmoke filters, can be used for distributing powder on a fiber surface.The devices are particularly suitable a) for applying the additives froma suspension in an aqueous liquid or a volatile, organic carrier or in aplasticizer liquid for the filaments, to which, in each case, a bindermay be added and b) for blowing the additive, consisting of smallparticles, onto the filaments, which may previously be wetted with anadhesive or a plasticizer. Alternatively or in addition, the adhesion ofthe particulate additives can be ensured by a melt adhesive, which isapplied either together with the particulate additives or separately oractivated by heating briefly.

The inventive tobacco smoke filter can be produced continuously,starting from filter rods, and cut to a limited length. Each individualelement of a length, limited in this way, could be used by itself as atobacco smoke filter for a cigarette. However, preferably, it is used ina longitudinally aligned arrangement with at least one further filterelement as part of an assembled (such as a double or triple) cigarettefilter. Preferably, a single filter element of the present invention isused in combination with a longitudinally aligned mouthpiece element ofthe usual appearance, for example, a uniform rod of cellulose acetatefiber cable.

The advantages, which are associated with the present invention, can besummarized as follows. It has turned out that, by adhering to theinventive teachings, finely divided additives can be introduced intotobacco smoke filters, and, at the same time, contrary to thecorresponding comparison product from the prior art, a particularly lowresistance to the passage of air can be noted during smoking. It wasfound that a particularly high filtration performance can be achievedwith the inventive filters.

Moreover, in comparison to the corresponding comparison products of thestate of the art, the inventive one-piece tobacco smoke filter can beproduced relatively easily. Moreover, the expensive production of theaforementioned chamber filter from several filter elements is omitted.It is a further advantage that, particularly when the filter material isconstructed from cellulose acetate, the taste of the smoke is evaluatedas particularly positive. A selective retention effect with respect tophenols is also observed.

The invention is described in greater detail below by means of examples.

EXAMPLE 1 Preparation of an Inventive Filter

A filter tow, having the specification 2,1Y48 (with a filament titer of2.33 dtex and a total titer of 53,333 dtex) is prepared on aconventional, two-step KDF drafting device of the Hauni Company, Hamburgand sprayed with 8% triacetin. After leaving the guide roller, thefilter tow web, with a minimum width of 250 mm is introduced into a pairof heated calender rollers and calendered with an effective linepressure of 40 kg/cm. The profiled calender rollers have a diameter of230 cm and a grooved width of 355 mm and have 10 profiled grooves percm, whereas the other roller is not profiled. They are heated to 150° C.with a silicone oil. The grilled profile is trapezoidal with an upperwidth of 0.4 mm and a depth of 0.5 miTL.

After leaving the calender rollers, the nonwoven, so prepared, is woundon a spool. Such a nonwoven spool is unwound at a conventional Foulardand passed through a bath, which is filled with an aqueous suspension ofactivated charcoal. In so doing, the nonwoven, directed downwards, isimmersed up to 5 cm in the suspension and then deflected upward at aguide roller. On leaving the suspension bath, the excess suspension issqueezed off by a pair of squeeze rollers. The squeeze rollers aredriven at a speed of 10 m/min and ensure uniform movement of thenonwoven through the suspension. After leaving the squeeze rollers, thenonwoven is passed through a recirculating air dryer at a temperature of150° C. The dryer has a drying segment of 4 meters and, with that,ensures the drying of the suspension and the fixing of the activatedcharcoal on the nonwoven.

Upon leaving the dryer, the nonwoven, doped with activated charcoal, isfolded into strands in a conventional commercial KDF 2 of the KorberCompany, Hamburg, by being introduced into an inlet nozzle, envelopedwith paper and cut to a filter length of 126 mm. The diameter of thefilter rods was adjusted to 7.8 mm.

COMPARISON EXAMPLE 1 Preparation of an Activated charcoal Filter byScattering Carbon Particles into a Filter Tow

A filter tow, having the specification 2,1Y48 (with a filament titer of2.33 dtex and a total titer of 53,333 dtex) is prepared on aconventional KDF 2 drafting device of the Hauni Company, Hamburg andsprayed with triacetin. Upon leaving the guide roller, the filter towweb with a minimum width of 200 mm is guided through a spreader nozzleand treated pneumatically with activated charcoal particles having aparticle size of approximately 250 μm. For this purpose, the activatedcharcoal powder is dosed continuously with a dosing balance onto anintake connecting piece and blown with compressed air through a pipelineto the spreader nozzle. Advantageously, the spreader nozzle is enclosedin a box with suction, which has openings only for the intake anddischarge of the filter tow web, in order to avoid any escape of carbondust into the surroundings. By matching the amount of activated charcoalsupplied to the speed of the filter tow web, the amount of activatedcharcoal on the filter tow web can be adjusted very accurately. Uponleaving the device described, the filter tow web is folded into strandsin an inlet nozzle and enveloped with paper in a conventional commercialKDF 2 of the Korber Company, Hamburg, at a strand speed of 50 m/min andcut to a filter length of 126 mm. The filter rod diameter was adjustedto 7.8 mm.

The results of measuring the resistance to airflow and the mass of theactivated charcoal are summarized in the Table.

Activated Particle Size Charcoal mass Resistance to Activated (mg per 21mm flow of air Charcoal Dpf Total of filter (filter plug) M_(ad)/ΔP (μm)(dtex) (dtex) plug (daPA) (mg/daPA) Comparison 250 2.33 53 80 131 0.61Example 1 333 Example 20 2.33 53 80 10 8.0 333

1. Tobacco smoke filters or filter elements, which are constructed inone piece and contain fibrous filaments or films based on polymers orpolymer mixtures, which can be spun or processed into films and containone or more additives, wherein a) the additives are present at thesurface of the fibers, the filaments or the films, b) the resistance ofthe tobacco smoke filter to the passage of air and the mass of theadditives in the tobacco smoke filter observe the following equation(I):M _(ad) /ΔP>1 mg/daPA   (I), in which ΔP_(7.8) is the resistance to thepassage of air (daPA), which is used as a value calculated on the basisof a 7.8 mm filter diameter, Ma_(d)(mg) is the mass of the additives,and c) the tobacco smoke filter has a channel structure and d) thefilter material is present as a two-dimensional formation.
 2. Thetobacco smoke filter of according to claim 1, wherein the filtermaterial is a two-dimensional formation of fibers or filaments or foldedfilm, the two-dimensional formation and/or the film being smooth,folded, embossed and/or partially consolidated.
 3. The tobacco smokefilter according to claims 1, wherein the filter material is built upfrom a cellulose ester.
 4. The tobacco smoke filter according to claim3, wherein the cellulose ester is cellulose acetate, cellulose butyrate,cellulose acetobutyrate, cellulose acetopropionate and/or cellulosepropionate.
 5. The tobacco smoke filter according to claim 4, whereinthe cellulose acetate has a degree of substitution of approximately 1.5and 3.0 and especially of 2.2 to 2.6.
 6. The tobacco smoke filteraccording to claim 1, wherein the ratio of M_(ad)/ΔP is more than 2mg/daPa and especially more than 3 mg/daPa.
 7. The tobacco smoke filteraccording to claims 1, wherein the additives, on the surface of thefibers, filaments or films are particulate, and, in particular, have aparticle size of less than 300 μm.
 8. The tobacco smoke filter accordingto claim 7, wherein the particle size of the additives is less than 100μm and especially less than 50 μm and particularly less than 30 μm. 9.The tobacco smoke filter according to claims 7, wherein the particulateadditives are porous additives, especially in the form of an absorbentbased on activated charcoal, metal oxides, metal hydroxides and/or metaloxide hydrates.
 10. The tobacco smoke filter according to claim 9,wherein the metal oxides, hydroxides and/or metal oxide hydrates arethose of aluminum, silicon, titanium and/or magnesium.
 11. The tobaccosmoke filter according to claims 9, wherein the porous additive istreated with active substances, especially in the form of antioxidants,flavors and/or antimutagenic substances.
 12. The tobacco smoke filteraccording to claims 1, wherein the additive, on the surface of thefibers, filaments and films, is a filtration aid, especially in the formof organic acids, acidic carboxylic esters of polyphenol and/orporphyrin derivatives.
 13. The tobacco smoke filter according to claims1, wherein the particulate additives are fixed on the surface of thefilter material by means of a binder, especially with polyvinyl acetate,polyvinyl alcohol, polyethylene glycol, water soluble esters or ethers,starch, starch derivatives and/or cellulose esters, especially celluloseacetate with an average degree of acetylation of 0.3 to
 1. 14. Thetobacco smoke filter according to claims 1, wherein the fibers,filaments or films of the film material contain further additives intheir interior to improve the properties.
 15. The tobacco smoke filteraccording to claim 14, wherein the further additives are plasticizers,marking agents, pigments and/or stabilizers.
 16. The tobacco smokefilter according to claim 15, wherein the plasticizer within the fibersor filaments or films is present in an amount of 5 to 15% by weight. 17.The tobacco smoke filter of according to claims 15, wherein theplasticizer is present in the form of triacetin, ethylene glycoldiacetate and/or diethyl citrate.
 18. The tobacco smoke filter accordingto claim 1, wherein the fiber weight (or filament weight/resistance tothe passage of air ratio S, related to the filament funnel, is largerthan about 0.7, the S value being calculated from the formulaS=(m _(A) /ΔP _(7.8))/dpf [10 m/daPA]  (II) in which m_(A) is the fiberweight (g), ΔP (daPA) is the resistance to the passage of air and dpf isthe titer of the filament (dtex) and, for the resistance to the passageof air, the value, calculated for a filter diameter of 7.8 mm, is used,and the hardness of the cigarette filter exceeds approximately 90filtrona hardness.
 19. The tobacco smoke filter according to claim 18,wherein the fiber weight does not exceed 10 mg/mm of filter lengthand/or the residual crimping of the filter material does not exceed thevalue of 1.45, Formula (III) applying here: I_(r)=10,000×m_(A)/(G×I)(III), in which m_(A) is the fiber weight (g), G is the total titer(g/10 exp 4×m) and I is the filter length (mm).
 20. The tobacco smokefilter according to claim 19, wherein the residual crimping is between1.05 and 1.4 and especially between 1.1 and 1.3.
 21. The tobacco smokefilter of according to claims 18, wherein the fiber weight (or filamentweight)/resistance to the passage of air ratio S, related to thefilament titer, does not exceed a value of about 2 and, in particular,has a value between 0.8 and 1.3.
 22. The tobacco smoke filter accordingto claim 18, wherein the fiber weight (or filament weight) is at least 4mg/mm of filter length and especially between 5 and 8 mg/mm of filterlength.
 23. The tobacco smoke filter according to claim 18, wherein thefiltrona hardness is between about 90 and 95 and particularly between 91and
 93. 24. The tobacco smoke filter according to claim 1, wherein thefilter contains a photoreactive additive, especially in the form offinely divided titanium oxide of the anatase type having an averageparticle size of less than 2 μm.